Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$69.75	12.476%	$78.452	$78.45	$78.45	$78.50
Purchase #2	$194.33	12.184%	$218.0072	$218.01	$218.00	$218.00
Purchase #3	$55.38	5.835%	$58.6114	$58.61	$58.60	$58.60
Purchase #4	$43.89	6.828%	$46.8868	$46.89	$46.90	$46.90
Purchase #5	$136.85	12.672%	$154.1916	$154.19	$154.20	$154.20
Purchase #6	$65.70	10.357%	$72.5045	$72.50	$72.50	$72.50
Purchase #7	$131.64	5.274%	$138.5827	$138.58	$138.60	$138.60
7 purchase totals =	$697.54		$767.2362	$767.23	$767.25	$767.30